[Preoperative localization of insulinoma is necessary]

Many insulinomas because of their small size are not localized by routine investigations: abdominal ultrasound, angiography, computed tomography, nor at the step of laparotomy. Biological diagnosis is far more encouraging. Percutaneous transhepatic sampling of blood in the portal venous system is very predictable for adenoma localization. Absolute reliability of this method remains to be established, nevertheless the observance of some basic requirements are already known: withdrawal of any drug interfering with insulin release several days before performing the catheterism; need of a steady, preferably low, glucose level during the whole sampling; selective samples in tiny draining veins of the whole gland, and adequate radio-immunoassay. Transhepatic sampling can detect multiple localisations and diffuse hyperplasia but angiography alone is able to show hepatic metastasis and is helpful in giving the surgeon information on local vascularization. Confrontation of both angiography and transhepatic sampling gives the best criteria of localization. In case of discrepancy, transhepatic sampling seems to be more reliable.